The major clincal objective is to study whether removal of leukemic cells from the autologous bone marrow graft has biological significance in vivo. This is studied in acute leukemia patients who are in second and subsequent remission, pretreated with a high dose combination chemotherapy regimen: CBV (Cytoxan, 6 gr M2; BCNU, 300 mmg/M2, and VP-16. 600 mg/M2 We plan to continue our clinical autologous bone marrow transplantation studies in second and subsequent remission patients. We will continue to study the hemopoietic restoration potential in vivo of hemopoietic precursor concentrates obtained by percoll density gradient centrifugation of marrow cell suspensions. The preparation of such concentrates is necessary to avoid clumping of the cells at time of immunocolloidal separation. At the end of the coming year we expect to have solid information concerning the in vivo hemopoietic restoration capability of such concentrates. Hopefully, we will already have initiated clinical studies at that time with purged marrow cell suspensions using the improved, modified immunoseparation procedure.